Sep. 17, 2010

Science Diction: Cell

The cell is the smallest, functional unit of life classified as a living thing. The human body, for example, contains more than 100 trillion, or 10^14 cells, with an average size of 10 micrometers and mass of 1 nanogram. But how did the word 'cell' come to be? Howard Markel, a a physician, medical educator, and historian of medicine at the University of Michigan, explains:

Given their tiny size, it is hardly surprising that a magnifying mechanism, in the form of a microscope, was required to identify these critical structures. The initial task fell to the famed British natural philosopher, Robert Hooke (1635-1703) while examining a thinly-cut piece of cork. In so doing, he noted a series of walled pores that "were not very deep, but consisted of a great many little boxes." They reminded him of the tiny rooms, or cellula (from Latin), occupied by monks; interestingly, the word recalls another Latin word, celare, which means to conceal or hide. From these root origins, the word, cell, made its literary debut in Hooke’s 1665 book, Micrographia.

Micrographia fascinated all who read it and led many budding scientists to purchase or make microscopes of their own. For example, in 1674, Anton van Leeuwenhoek of Delft (1632-1723) described the first living celled organism. Peering through his microscope at a colony of algae, Spirogyra, he was amazed to see "little animals" swimming about. He called them "animalcules."

For the better part of a century and a half, however, cells remained more objects of observational entertainment than experimental science. It was not until the early 19th century that a cadre of German scientists including Theodor Schwann (1810-1882), Matthias Schleiden (1804-1881), Robert Remak (1815-1865), and, most notably, Rudolf Virchow (1821-1902) developed a novel notion they called cell theory. After much debate and research, these men emphatically declared two revolutionary ideas: 1) cells were the basic unit of all living things; and 2) Omnis cellula e cellula, or all cells come from other cells just like it, by means of cell division. The latter was essential in debunking the prevailing theory of spontaneous generation—the notion that living organisms could arise from non-living, and typically organic, matter such as decaying meat.

In 1858, Rudolf Virchow published his path-breaking book, Cellular Pathology. Beginning with the premise of "omnis cellula e cellula," Virchow demonstrated that normal cellular function depended on a number of intracellular physical and chemical changes. More importantly, he asserted that all disease was the result of a deviation from normal cellular structure and function.

Initially, many doctors and patients had difficulty accepting Virchow’s ideas. Recall, that medicine of this era was rooted in humoralism, the ancient Hippocratic theory that all diseases arose from an imbalance of the four bodily humors—yellow bile, black bile, blood, and phlegm—rather than individual organs. Scoffing at the idea that disease rested within aberrant cells, many insisted that illness could only be arrested by resolving humoral imbalances by means of blood-letting or doses of powerful purgatives and emetics.

In the century and a half that followed, reams of reproducible evidence have overwhelmed such antiquated explanations. Indeed, the modern scientific contemplation of cells—and the organelles, proteins, molecules and genetic material they comprise—is the foundation for understanding biology, pathology, medicine, and biotechnology.

How amazing that such a productive field of scientific inquiry began with a glorified magnifying glass and a thin slice of cork!

In this segment, we'll talk about the origins of the word 'cell' and the history of its meaning.